The field of biomechanics, including implanted medical devices, is constantly growing. Today, implants are no longer limited to static parts, simply replacing damaged, diseased or surgically removed tissue, organs, or limbs of the body. Instead, a growing number of implants combine advanced electronic, mechanic and in many cases, hydraulic mechanisms, mimicking or replacing functions of the body, supporting or even augmenting functions of the body.
The hydraulic mechanism can be one of compression or restriction, achieved by a hydraulic member acting on at least one body part, organ or tissue. The hydraulic mechanism can also be one of actuation, where a hydraulic member causes a body part to move. The hydraulic mechanism can also be one of filling, extending, applying torque, expanding or otherwise adjusting body parts, organs or tissue, where the hydraulic member acts on the size, shape or position of a body part, organ or tissue.
One example is the adjustable gastric band (disclosed for example in WO 00/00108) used e.g. in the treatment of obesitas. In this example, a band is surgically placed around the stomach, reducing the opening in the cardia region, or around the stomach, creating a small gastric pouch, both methods effectively limiting the food intake of the obese subject. An adjustable gastric band has a considerable advantage: the tightness of the gastric band can be adjusted without the need for repeated operations. Hydraulic gastric bands are one sub-group of adjustable gastric bands. The tightness of the band is adjusted by injecting or withdrawing a fluid present inside the band. This can be controlled within the body, through the provision of a reservoir of said fluid, coupled to a pump or similar device. Alternatively, the fluid can be injected or withdrawn externally, for example through an access port or injection port. When fluid is introduced, the band places pressure around the outside of the stomach, restricting the movement of food. Frequently the tightness of the band is adjusted during several visits to the doctor, until optimal restriction has been achieved. There are currently several gastric bands on the market, so far however regulated through an injection port.
Other types of hydraulic implants include artificial sphincters for controlling the flow in various ducts in the body, e.g. the anal, urethral, pancreal or bile ducts; artificial valves controlling the blood flow to different body parts; hydraulic corpus cavernosum implants for treating erectal dysfunction; hydraulic implanted braces for vertebral adjustments, such as the treatment of scoliosis; adjustable breast implants etc, all products which are currently in different phases of development, testing or use. A non-exclusive list of examples includes the male sexual impotence treatment apparatus described in EP 1 563 814 B1, the anal incontinence treatment apparatus described in EP 1 584 303 B1, and the hydraulic urinary incontinence treatment apparatus described in EP 1 263 355 B1.
In all hydraulic applications, implanted or not, there is a small risk of rupture of membranes, tubing, couplings, connectors, pumps and valves etc, and consequently a leakage of the hydraulic fluid used may take place. Also other implants, functioning through mechanical or electrical mechanism may loose their integrity and suffer from ruptures, leaks and the like. In an implanted device, a leakage may be particularly problematic, both as it is more difficult to detect, and as a leakage can have negative consequences for the patient's health. In many cases, saline is used in order to minimize the consequences of possible leaks. Even when the leakage itself does not constitute a health issue, the function of the implant will be impaired. A leaking hydraulic implant will inevitably loose its internal pressure, which in turn influences its function. The implant will no longer retain its desired volume, shape or position. For example a hydraulic implanted brace will no longer act on the vertebrae with the same force and will not be able to retain the desired position. Similarly, a hydraulic implanted artificial sphincter will no longer be able to prevent leakage of urine or faeces.
While immediate repair or replacing the implant would be the most desirable action, it is perhaps not always possible. It may be difficult to schedule an operation, or the patient may be too weak to undergo anaesthesia and surgical intervention. For these and other reasons, it would be desirable if a leaking implant could be repaired, permanently or temporarily, without the need of hospitalizing the patient.
In an entirely different technical field, namely the automotive industry, different solutions for repairing tires have been developed. According to one principle, the punctured tire is filled with a propellant and a foam-forming sealant material which expands and cures inside the tire, restoring the shape and pressure of the tire. According to another principle, a solution is introduced through the valve and forms a sealing layer, or lining, on the inside of the tire, where after the tire can be inflated again. In a combination of the two principles, the foam also acts as a sealant.
In the first case, the foam forming material is usually polyurethane. Other examples include polyisoprene and ethylene-propylene-diene terpolymer elastomer (EPDM).
In the second case, a polymer solution including for example polybutene, polypropylene or butyl rubber is used. Alternatively, a thixotropic polymer gel is used. Examples of such gels include, but are not limited to, acrylic polymers. The thixotropic properties of the gel make it possible to introduce it through the valve, and when the tire rotates, the gel will spread evenly over the inner surface. When the vehicle stops, the gel will become more rigid and substantially remain evenly spread inside the tire.
These repair kits and solutions are commercially available and frequently included in new cars, as a space and weight saving alternative to the traditional spare tire.
WO 2004/052248 discloses a method and apparatus for intervertebal disc expansion, wherein a biomaterial is injected into an intradiscal space where it undergoes transition from a flowable to a non-flowable state. The biomaterial can be injected directly into a space within the disc annulus, or into a balloon-like element introduced into the disc annulus.
WO 2007/133214 discloses devices for prosthetic disc replacement and soft-tissue reconstruction wherein an implanted device is inflated with a suitable gallant or combination of gellants. The disclosure of the '214 publication addresses the issue of leaking implants and teaches the use of gel forming fillers, where a flexible empty or partially filled pouch is implanted into a selected site in a human body, where after at least one type of gallant is injected into the pouch, wherein the gallant solidifies within the pouch and forms a solidified medical device of a desired shape.
US 2005/0015140 A1 relates to three-dimensional space filling implantable devices which may be filled with an bioactive agent. The '140 publication and describes an encapsulation device configured to receive a fluid to expand the device to conform to the shape. An important aspect of said device is a self-sealing valve, configured to open to receive one or more fluids and close to prevent leakage into the body.
WO 01/87195 concerns a method and apparatus for treating interverbal disks, describing the heating and injection of thermoplastic material, e.g. gutta percha, either directly into an existing cavity in the body, or into a cavity created by expanding an expandable member. The heated thermoplastic material is flowable at an elevated temperature, but solidifies at body temperature.
There remains a need for improved methods and compositions. Further, the background art does not address problems encountered with implants having more complex functions. Thus, one objective underlying various embodiments of the invention is to make it possible to repair and/or stabilize, temporarily or permanently, a leaking implanted device, such as an implanted hydraulic device.
Another objective is to stabilize an implanted device, for example in the sense that the position, shape or volume of the device or a hydraulic element forming part of the device, is permanently fixed.
Further objectives of the invention, as well as advantages associated with embodiments of the invention, will become evident to a skilled person upon a closer study of the present description, non-limiting examples, claims and drawings.